Detection methods for particular biological molecules (bio-molecule) are manifold and many different approaches are presently available to the skilled person. The detection of specific biological molecules has a range of important practical applications, including gene identification for diagnostic purposes.
In general, the detection of biological specimen (the “target”) such as polynucleotides, DNA, RNA, cells, and antibodies can especially be performed on an array for example a so-called bio-array (or micro-array) whereupon corresponding probe molecules are attached at various sites on the array. Target-probe examples include: DNA/RNA-oligonucleotide, antibody-antigen, cell-antibody/protein, hormone receptor-hormone, etc. When the target is bound or hybridized to a corresponding probe molecule, detection of the target bio-molecule may be performed by a variety of optical, electronic and even micromechanical methods.
A commonly used technique for detection of molecular binding on bio-arrays is optical detection of fluorescent labeled targets also known as a “label” or “marker”. In general, a label may be any agent that is detectable with respect to its physical distribution and/or the intensity of the outgoing signal it gives. Fluorescent agents are widely used, but alternatives include phosphorescent agents, electroluminescent agents, chemiluminescent agents, bioluminescent agents, etc.
In general a problem of luminescence detection relates to separating the luminescent light with low intensity from the illuminating non-luminescent light, generally with high intensity. The reliability of luminescence detection therefore depends much on the optical characteristics of the spectral filters that are used in the separation process. The spectral filter function may include two steps: a first filter (called the ‘excitation filter’) preferably transmits the rays with a wavelength overlapping with the excitation spectrum of the label and blocks all rays with a wavelength that is inside the spectrum of the detection window. A second filter (called the ‘emitter filter’ or ‘detection filter’) preferably blocks all illumination light and transmits only the luminescent rays. The attenuation (blocking power) of a typical filter set is better than 10−6. To this end, also the optical properties of the substrate may be considered.
US 2005/0048571 discloses a substrate for reducing the auto-fluorescence in connection with optical detection from bio-arrays. In the disclosure, a porous layer of the substrate is tinted with a colorant agent. A drawback of the tinting of the substrate is however that it renders the substrate more expensive, and it may limit the number of different types of substrates that may be used.
The inventor of the present invention has appreciated that improved means for luminescence detection would be of benefit, and has in consequence devised the present invention.